JP3521535B2 - Aerobic biological treatment system for organic wastewater - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerobic biological treatment apparatus for organic drainage, and more particularly to an aerobic biological treatment apparatus for organic drainage equipped with means for reducing excess sludge.

[0002]

2. Description of the Related Art An aerobic treatment method for treating organic wastewater under aerobic conditions by utilizing the action of aerobic microorganisms, such as an activated sludge treatment method, produces a large amount of hardly dehydratable excess sludge. It is difficult to generate and process. Conventionally, such excess sludge has been disposed of, but it is difficult to secure a disposal site for it, and it is necessary to reduce the volume of sludge.

In Japanese Patent Laid-Open No. 6-206088, an amount of biological sludge larger than the amount of sludge that grows due to assimilation of BOD in the liquid to be treated is withdrawn from the aerobic biological treatment system, and the extracted sludge is subjected to ozone treatment and then preferably. The aerobic biological treatment method of the organic waste liquid introduced into the aerobic biological treatment system is described, and FIG. 4 is a system diagram of the treatment device. In FIG. 4, 1 is an aerobic biological treatment system, 2 is a reforming treatment system, and the aerobic biological treatment system 1 comprises an aeration tank 11 and a solid-liquid separation device 12. An air diffuser 15 is provided at the bottom of the aeration tank 11,
The air supply path 16 is in communication. The aeration tank 11 has a liquid passage 17 to be treated and a return sludge passage 2 having a pump 23.
4 is in touch. A communication path 18 communicates with the solid-liquid separation device 12 from the aeration tank 11. A treatment liquid passage 21 and a separation sludge discharge passage 22 are connected to the solid-liquid separation device 12.
The separated sludge discharge path 22 includes a return sludge path 24 and a withdrawn sludge path 32.
And the excess sludge discharge path 37 is branched.

The reforming treatment system 2 reforms sludge to be easily biodegradable by ozone treatment, has an ozone treatment tank 31, and has an extraction sludge passage 32 communicating with the solid-liquid separation device 12 at the upper part and an exhaust sludge. The ozone passage 33 communicates with the ozone supply passage 34 and the ozone treatment sludge passage 35 communicates with the lower portion. The ozone treatment sludge passage 35 communicates with the aeration tank 11. A pump 36 is provided in the extraction sludge passage 32.

In order to aerobically treat the organic waste liquid with the apparatus shown in FIG. 4, first, the liquid to be treated is introduced into the aeration tank 11 from the liquid to be treated 17 and the return sludge and the sludge to be returned from the return sludge passage 24. The aerobic biological treatment is performed by mixing with the biological sludge in the aeration tank 11 and aerating the air supplied from the air supply passage 16 from the air diffuser 15. A part of the mixed liquid in the aeration tank 11 is introduced into the solid-liquid separation device 12 through the communication path 18 and is separated into the separated liquid and the separated sludge. The separated liquid is discharged from the treated liquid passage 21 as a treated liquid, a part of the separated sludge is returned to the returned sludge passage 24 or the aeration tank 11 as a returned sludge, and the other part is ozone-treated from the drawn sludge passage 32 as a drawn sludge. Supply to tank 31,
When excess sludge is generated, it is discharged from the excess sludge discharge path 37 to the outside of the system.

In the reforming treatment system 2, a part of the separated sludge is introduced into the ozone treatment tank 31 as the drawn sludge from the drawn sludge path 32. Here, ozone is supplied from the ozone supply path 34,
Ozone treatment is performed by bringing ozone into contact with the drawn sludge. As a result, most of the living bacteria in the drawn sludge are killed, and the sludge becomes B
It is converted into OD and easily biodegradable. The ozone-treated sludge is circulated from the ozone-treated sludge passage 35 to the aeration tank 11 for aerobic biological treatment. After ozone treatment of drawn sludge in this way, it is possible to reduce the volume of surplus sludge by aerobic biological treatment, and by ozone treatment of more drawn sludge than multiplication sludge, the amount of excess sludge generated can be reduced. It can be zero.

[0007]

However, in the above-mentioned conventional method, since the living bacteria are killed by the ozone treatment, the average sludge retention time (SRT) represented by the following formula, which is focused on the living bacteria, becomes short. SRT = A / B of living bacteria (a) (In the formula, A indicates the amount of sludge held in the aeration tank, and B indicates the amount of ozone-treated sludge.)

For example, when the amount of surplus sludge generated is set to zero, about three times the sludge generated as a surplus sludge produced by a normal activated sludge process is ozone-treated as a drawn-out sludge. SRT (Hereafter, live bacteria S
(RT is called SRT ') is shortened to about 1/3. For this reason, in the conventional method, when the water temperature is low in winter, the decomposition of organic matter becomes insufficient and the treated water quality becomes unstable, and undecomposed organic sludge accumulates in the sludge flocs, which may cause aeration tanks and solidification. The sludge settability in the liquid separation tank may deteriorate.

Such a problem can be solved by adding an aeration tank and reducing the sludge load, but the expansion of the space and the construction cost are remarkable, and the economic constraint is large.

In order to solve the above problems, the object of the present invention is to reduce the volume of surplus sludge, to suppress the expansion of the installation space and the construction cost, and to carry out a stable treatment using a small apparatus. It is an object of the present invention to provide an aerobic biological treatment device for organic wastewater, which can obtain water quality and can improve sludge sedimentation.

[0011]

The present invention is the following aerobic biological treatment apparatus for organic waste liquid. (1) Accepts the organic waste liquid and the mixed liquid of the second aeration tank
A first aeration tank that mixes with the biological sludge in the tank to aerate, a solid-liquid separation device that separates the mixed liquid of the first aeration tank into a separation liquid and separation sludge, and the solid-liquid A reforming treatment device for reforming a part of the separated sludge separated by the separation device or a part of the mixed liquid of the first aeration tank to make it easily biodegradable, and a reforming device reformed by the reforming device. Return sludge of quality treated sludge and other part of separated sludge discharged from the solid-liquid separation device
An aerobic biological treatment apparatus for organic waste liquid, comprising: a second aeration tank that mixes mud to aerate and returns the aeration liquid to the first aeration tank. (2) The aerobic biological treatment apparatus for organic waste liquid according to the above (1), wherein the reforming treatment apparatus is an ozone treatment apparatus.

The organic waste liquid to be treated in the present invention is a waste liquid containing an organic substance treated by a usual aerobic biological treatment method, but contains an organic substance or an inorganic substance which is hardly biodegradable. May be. Examples of such organic effluents include sewage, night soil, food factory effluents and other industrial effluents.

The first aeration tank in the apparatus of the present invention receives the organic waste liquid and the liquid mixture of the second aeration tank described later,
This is a tank that mixes with the biological sludge in the tank and aerates it to perform aerobic biological treatment. The solid-liquid separation device in the device of the present invention is a device for performing solid-liquid separation of the mixed liquid in the first aeration tank into separated liquid and separated sludge. As such a solid-liquid separator, for example, a solid-liquid separator using precipitation, levitation, centrifugation or a membrane can be used.

The reforming apparatus in the apparatus of the present invention is a sludge that has been separated by the solid-liquid separation apparatus or a mixed solution of the first aeration tank (hereinafter, these are referred to as drawn sludge) to be easily biodegradable. It is a device that does. Examples of such a reforming treatment apparatus include, for example, an ozone treatment apparatus for subjecting drawn sludge to ozone treatment for reforming, an acid treatment apparatus for treating with acid treatment for reforming, an alkali treatment apparatus for treating with alkali treatment for reforming, and a heat treatment treatment. It is possible to use a heat treatment device for reforming by using a heat treatment device, a treatment device combining these devices, or the like. Of these, the ozone treatment device is preferable.

Of these reforming treatment apparatuses, the ozone treatment apparatus will be described first. An ozone treatment device as a reforming treatment device is a device for bringing drawn sludge into contact with ozone, and the sludge is reformed to be easily biodegradable by the oxidizing action of ozone. As the ozone treatment device, an ozone treatment tank for bringing ozone into contact with sludge in the sludge-containing liquid to cause an oxidation reaction, and a device having means for introducing the ozone-treated sludge into the second aeration tank Devices of any configuration can be used. As the contact method in this case,
A method of introducing sludge into the ozone treatment tank and blowing ozone, a method of mechanical stirring, a method of utilizing a packed bed, and the like can be adopted. If sludge tends to settle in the ozone treatment tank, or if there is more sludge settling than floating sludge,
It is preferable that the sludge-containing liquid and ozone are brought into contact with each other in parallel flow, which improves the contact efficiency between the sludge and ozone. On the other hand, when the sludge easily floats in the ozone treatment tank, or when there is more sludge floating than the sedimenting sludge, it is preferable to bring them into contact with each other in a counterflow, which improves the contact efficiency.

When ozone is blown into the ozone treatment tank to perform ozone treatment, foaming occurs, but in order to prevent troubles due to this foaming, a liquid spraying means for defoaming can be provided in the ozone treatment tank. As the liquid spraying means, it is preferable to use a device configured to draw out a tank liquid containing sludge in the ozone treatment tank and spray the drawn liquid as defoaming water on the liquid surface in the ozone treatment tank.

Further, as an ozone treatment tank, a liquid-phase contact area for blowing ozone into drawn sludge for gas-liquid contact is formed in the lower part of the tank, and a foam contact area for contacting foamed foam and ozone is formed on the upper part thereof. The use of an ozone treatment tank configured to be formed further enhances ozone treatment efficiency. The height of the liquid-phase contact area is 0.2 to 3 m, preferably 0.
5 to 1.5 m. The height of the foam contact area may be 1 m or more above the liquid surface of the drawn sludge in the liquid phase contact area, but is preferably 1 to 10 m, more preferably 2 to 5 m.

A foam retaining member can be filled in the foam contact area, whereby when the inside diameter of the ozone treatment tank is large and it is difficult to retain the foam, or the concentration of the biological sludge is low, the extracted sludge is unlikely to foam. Even in such a case, the foam can be efficiently retained and the ozone treatment efficiency can be increased. The foam holding member may have a structure capable of holding foam, but a partition plate structure such as a honeycomb shape or a lattice shape is preferable.

The above-mentioned liquid spraying device is provided above the foam contact area in the ozone treatment tank to collect industrial water, final treatment liquid, drawing liquid from the ozone treatment tank, or a mixed liquid of the drawing liquid and the liquid to be treated. It can be sprayed towards the foam layer, which can prevent excessive foaming and maintain the foam contact area at a predetermined height. In this case, it is preferable to use a drawing liquid or a mixed liquid of the drawing liquid and the liquid to be treated because the sludge concentration of the liquid in the tank does not decrease and the nozzles and the like are not clogged. Since the foam contact area of the ozone treatment tank is only filled with foam, the strength of the ozone treatment tank may be smaller than that of an apparatus that fills the inside of the tank with the liquid to be treated, and the ozone treatment apparatus becomes a low cost accordingly.

When the ozone treatment is carried out in an acidic region of pH 5 or less, the efficiency of oxidative decomposition increases. The pH adjustment at this time is
It is preferable to add an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid as a pH adjusting agent to the drawn sludge, to adjust the drawn sludge by acid fermentation, or to perform a combination thereof. p
When the H adjuster is added, the pH is preferably adjusted to 3 to 4, and when the acid fermentation treatment is performed, the pH is preferably adjusted to 4 to 5. The ozone treatment can be carried out by bringing the drawn sludge or the acid fermentation treatment liquid as it is, or by concentrating it with a centrifuge or the like, if necessary, adjusting the pH to 5 or less, and contacting it with ozone.

As ozone, besides ozone gas, ozone-containing gas such as ozone-containing air or ozonized air can be used. The amount of ozone 0.002~0.05g-O ₃ /
g-VSS, preferably 0.005~0.03g-O ₃
/ G-VSS is desirable.

Next, an acid treatment device as a reforming treatment device will be described. The acid treatment device adds mineral acids such as hydrochloric acid and sulfuric acid to the drawn sludge, and the pH is 2.5 or less, preferably pH 1-2.
This is an apparatus for reforming by staying for a predetermined time under the acidic condition of. As the acid treatment apparatus, any configuration apparatus can be used as long as it has a reforming tank for reforming drawn sludge and a means for introducing the acid-treated sludge into the second tank air tank. be able to. As the residence time in the reforming tank,
For example, it is set to 5 to 24 hours. At this time, it is preferable to heat the sludge, for example, to 50 to 100 ° C., since the reforming is promoted. The sludge is easily biodegradable by such an acid treatment.

The alkali treatment apparatus as a reforming treatment apparatus is an apparatus for adding 0.1 to 1% by weight of alkali such as sodium hydroxide and potassium hydroxide to drawn sludge, and allowing it to stay for a predetermined time for reforming. is there. As the alkali treatment device, any device having any structure can be used as long as it has a reforming tank for reforming drawn sludge and a means for introducing the alkali-treated sludge into the second aeration tank. it can.
The residence time in the reforming tank is, for example, 0.5 to 2 hours. At this time, the sludge is heated, for example, 50 to 100 ° C.
It is preferable that the heating is performed because the reforming is promoted. The sludge is easily biodegradable by such alkali treatment.

The heat treatment apparatus as the reforming treatment apparatus is an apparatus for retaining the drawn sludge at a predetermined temperature, for example, 70 to 100 ° C. for a predetermined time, for example, 2 to 3 hours to reform the sludge.
As the heat treatment device, a device having any structure can be used as long as it has a reforming tank for reforming the drawn-out sludge and a device for introducing the heat-treated sludge into the second aeration tank. However, it is preferably used in combination with an acid treatment device or an alkali treatment device. The sludge is easily biodegradable by the heat treatment.

The second aeration tank in the apparatus of the present invention receives the reformed sludge reformed by the reforming apparatus and a part of the separated sludge discharged from the solid-liquid separation apparatus (return sludge). A tank having means for mixing with the biological sludge in the tank and aeration, and returning this aeration liquid to the first aeration tank. Here, the first aeration tank and the second aeration tank may be provided as separate independent tanks, or one tank may be divided into a second aeration tank in the front stage and a first aeration tank in the rear stage. Can also be configured as. The volume ratio of the first aeration tank to the second aeration tank is 9: 1 to 4: 6, preferably 8: 2 to 5: 5.

[0026]

In the reforming apparatus, the drawn-out sludge is reformed into easily biodegradable organic matter by the reforming treatment such as ozone treatment, acid treatment, alkali treatment or heat treatment. By introducing the modified sludge and other part of the separated sludge into the second aeration tank and mixing them with the biological sludge in the tank for aeration, aerobic microorganisms rapidly grow and the amount of MLSS increases. Will increase. The first aeration tank receives the organic drainage liquid and the aeration liquid (mixed liquid) from the second aeration tank, mixes it with the biological sludge in the tank, and aerates it to remove the organic substances and organic matter in the organic drainage liquid. The organic matter modified to be easily biodegradable by the quality treatment is aerobically biodegraded. In both the first and second aeration tanks, organic matter is decomposed and aerobic microorganisms grow, but mainly the organic matter is decomposed in the first aeration tank and aerobic in the second aeration tank. Rapid growth of microorganisms occurs.

In the apparatus of the present invention, since the first and second aeration tanks are provided, even if the total volume of the aeration tanks is the same as in the conventional apparatus having only the first aeration tank, The SRT (SRT ') of living bacteria becomes longer. Therefore, a long time is required for decomposing the organic matter, whereby stable treated water quality can be obtained, and sludge settability is improved. The effect of increasing the SRT 'is obtained by switching the conventional device operating the MLSS concentration of the aeration tank at a low concentration to the device of the present invention and the conventional device operating the MLSS concentration at a high concentration. Compared with the case of switching to the device of the invention, the former is larger.

The principle of sludge volume reduction in the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram for explaining the principle of sludge volume reduction. In the figure, 1 is an aerobic biological treatment system,
2 is a modification processing system. The aerobic biological treatment system 1, like an activated sludge treatment device, is a treatment system that aerobically decomposes an organic waste liquid by contacting it with biological sludge, and solid-liquid separation from the first and second aeration tanks. Although the apparatus and the apparatus are separately provided, they are shown as an overall processing system including them.

The aerobic biological treatment system 1 of FIG. 1 holds a certain amount of biological sludge 3a for aerobic biological treatment. When the liquid to be treated 4 is introduced into the aerobic biological treatment system 1 to perform aerobic biological treatment, the BOD contained in the liquid to be treated 4 is assimilated into the biological sludge 3a, and the sludge 3b newly produces the sludge 3b. Is generated. On the other hand, biological sludge 3a in the system
The self-decomposition causes the self-decomposition 3c to disappear. Therefore, in the steady state, the difference between the produced sludge 3b and the self-decomposition 3c grows as the grown sludge 3d.

A case in which the breeding sludge 3d is treated as surplus sludge by the reforming treatment system 2 is shown by a broken line 5 in FIG. 1, but when the breeding sludge 3d is reformed and returned to the aerobic biological treatment system 1. , BOD generated by the reforming process is converted to sludge,
Another generated sludge 3e is generated, and this sludge becomes a substantial sludge multiplication component, which must be discharged as surplus sludge.
On the other hand, the amount of extracted sludge 3f is larger than that of the propagated sludge 3d
BOD produced by the reforming treatment by extracting the reformed sludge 6 from the aerobic biological treatment system 1 and converting it to BOD by the reforming treatment system 2 and returning the reformed sludge 6 to the aerobic biological treatment system 1.
From this, another 3 g of generated sludge is generated. In this case, the difference between the drawn sludge 3f and the produced sludge 3g becomes the mineralized portion 3h.

By reforming the extracted sludge 3f in an amount larger than that of the breeding sludge 3d and converting it into BOD, the mineralized portion becomes larger than in the case of reforming only the breeding sludge 3d. The volume reduction rate is high. If the amount of drawn sludge 3f is determined so that the multiplied sludge 3d and the mineralized portion h are equal, the excess sludge becomes substantially zero. Breeding sludge 3
When d is larger than the mineralized portion 3h, the difference becomes a substantially increased portion 3i and is discharged outside the system as excess sludge 7. Reference numeral 8 is a treatment liquid of the aerobic biological treatment system 1.

In the aerobic biological treatment system 1, the aeration tank capacity is V, the biological sludge concentration is X, the sludge yield is Y, the treated liquid flow rate (treatment liquid flow rate) is Q, and the organic matter concentration of the treated liquid is C.
i, organic concentration of treated liquid is Ce, concentration of biologically treated organic substance is (Ci-Ce), sludge self-decomposition constant is Kd, excess sludge discharge amount is q, extraction amount to reforming treatment device is Q ', The mass balance is represented by the following equation [1], where k is the rate at which the quality-treated sludge is converted back to biological sludge.

[Equation 1]     VdX / dt = YQ (Ci-Ce) -VKdX-qX-Q'X + kQ'X [1]

In the equation [1], VdX / dt is the amount of change in the biological sludge 3a in the aerobic biological treatment system 1, YQ (Ci-C).
e) is the amount of generated sludge 3b, VKdX is the amount of self-decomposition 3c,
qX represents the amount of surplus sludge discharged, Q'X represents the amount of extracted sludge 3f, and kQ'X represents the amount of produced sludge 3g. Here, Q (Ci-Ce) / V = LV (tank load), q / V = 1 / SR
If T (excess sludge retention time ratio), Q ′ / V = θ (circulation ratio of biological sludge to the reforming treatment system), and (1−k) = δ (mineralization rate) are set, in the steady state, [ The equation 1] is simplified as the following equation [2].

[Equation 2]     YLV / X = Kd + 1 / SRT + δθ [2]

In the usual aerobic biological treatment system in which the reforming treatment system 2 does not exist, the third term (δθ) of the formula [2] does not exist, so
When the sludge load is constant, the excess sludge (X / SR
T) is determined. On the other hand, in the treatment system in which the reforming treatment is combined, as is apparent from the equation [2], the excess sludge is reduced in volume by the value of the third term. Under the condition that the value of the third term is comparable to the value of the second term, the sludge load can be set to a normal value without discharging the excess sludge (1 / SRT = 0). is there.

Explaining in detail the case where the reforming treatment is ozone treatment, the parameters of the third term in the above equation [2] are the mineralization rate δ and the circulation ratio θ, of which δ is the ozone injection rate to sludge. Is 0.01 g-O ₃ / g-VSS or higher, the steady value is around 0.5, and thus the apparent volume reduction rate of sludge is determined in proportion to θ in this region. On the other hand, the circulation ratio θ does not affect the sludge activity up to about 0.5 day ^-1 . This means that the sludge activity of the aerobic biological treatment system 1 is maintained even if less than 1/2 of the biological sludge 3a retained in the aerobic biological treatment system 1 is circulated to the ozone treatment system as drawn sludge 3f per day. Is meant to be done.

Therefore, the upper limit of the circulation ratio θ is 0.5 day ^-1.
It is said that When θ is zero, the complete oxidation method is used, but in this case the sludge load is low and the volume reduction effect is small.
When the amount of the extracted sludge 3f is the same as the amount of the grown sludge 3d, the volume reduction rate is the same as that of the conventional method. In normal aerobic biological treatment, SRT is 10 days and sludge extraction rate is 0.1 day ^-1 . In the present invention, the amount of drawn sludge 3 which is more than that of 3d
When circulating f, the lower limit of the circulation ratio θ is a value greater than 0.1Day ^-1, may preferably be 0.2Day ^-1 or more, when a particular 0.3Day ^-1, excess sludge does not occur 100% volume reduction is possible.

[0037]

EXAMPLES Next, examples of the present invention will be described. Figure 2
FIG. 3 is a system diagram showing an aerobic biological treatment apparatus of the present invention, which is an example in which ozone treatment is adopted as a reforming treatment. In FIG. 2, reference numeral 1 denotes an aerobic biological treatment system, which comprises an aeration tank 11 and a solid-liquid separation device 12. A partition plate 13 is provided in the aeration tank 11 and is divided into a first aeration tank 11a and a second aeration tank 11b. The second aeration tank 11b and the first aeration tank 11a are connected to each other through the flow path 14, and the mixed liquid in the second aeration tank 11b is configured to flow into the first aeration tank 11a through the flow path 14. ing. Air diffusers 15a and 15b are provided at the bottoms of the first and second aeration tanks 11a and 11b, respectively, and air supply passages 16a and 1a are provided.
6b is in touch. A liquid passage 17 to be treated communicates with the first aeration tank 11a, and a communication passage 18 communicates with the solid-liquid separation device 12 from the first aeration tank 11a. Solid-liquid separator 1
A treatment liquid passage 21 and a separated sludge discharge passage 22 are connected to the unit 2. A return sludge passage 24 having a pump 23 branches from the separated sludge discharge passage 22 and communicates with the second aeration tank 11b.

The reforming treatment system 2 reforms sludge to be easily biodegradable by ozone treatment, has an ozone treatment tank 31, and has a withdrawal sludge passage 32 and an exhaust ozone passage 33 branched from the separated sludge discharge passage 22. Contacted the upper part, ozone supply line 34
The ozone treatment sludge path 35 communicates with the lower part. The ozone treatment sludge path 35 communicates with the second aeration tank 11b from the ozone treatment device 31. A pump 36 is provided in the extraction sludge passage 32. 37 is a surplus sludge discharge path.

In order to aerobically treat the organic waste liquid with the apparatus shown in FIG. 2, the liquid to be treated is first introduced into the first aeration tank 11a from the liquid passage 17 to be mixed with the biological sludge in the tank. The air supplied from the first air supply passage 16a is diffused from the first diffuser 15a to perform aerobic biological treatment. Here, organic matter is mainly decomposed by bio-oxidation reaction, and sludge grows.

A part of the mixed liquid in the first aeration tank 11a is introduced into the solid-liquid separation device 12 through the communication path 18, and is separated into the separated liquid and the separated sludge by the sedimentation separation. The separated liquid is discharged as a processing liquid from the processing liquid passage 21 to the outside of the system. The separated sludge is discharged from the separated sludge discharge passage 22, and a part of the separated sludge is introduced as return sludge into the second aeration tank 11b from the return sludge passage 24 by driving the pump 23.

The other part of the separated sludge is introduced as the extracted sludge into the ozone treatment tank 31 through the extraction sludge passage 32 by driving the pump 36. Here, ozone is supplied from the ozone supply passage 34, ozone is brought into contact with the drawn-out sludge, and is subjected to ozone treatment, so that the sludge is easily biodegradable. As a result, most of the living bacteria in the drawn sludge are killed, and the sludge becomes BOD. The ozone exhaust gas is discharged from the exhaust ozone passage 33. The ozone-treated sludge is discharged from the ozone-treated sludge passage 35 to the second aeration tank 1
Circulate to 1b. When excess sludge is generated, it is discharged from the excess sludge discharge path 37 to the outside of the system.

In the second aeration tank 11b, a part of the separated sludge (return sludge), the ozone-treated sludge and the biological sludge in the tank are mixed, and the air supplied from the second air supply passage 16b is mixed with the second sludge. Air is diffused from the air diffuser 15b to perform aerobic biological treatment. Here, although organic substances are also decomposed by the biooxidation reaction, sludge is mainly grown. Second aeration tank 11
The mixed liquid in b is returned from the flow path 14 to the first aeration tank 11a.

As described above, according to the present invention, the aeration tank 11 is divided into the first aeration tank 11a and the second aeration tank 11b.
After the returned sludge and the ozone-treated sludge are subjected to aerobic biological treatment in the second aeration tank 11b, this aerobic treated liquid is introduced into the first aeration tank 11a and mixed with the liquid to be treated for further aerobic biological treatment. Since it is configured as described above, the amount of sludge held in the entire aeration tank 11 increases as compared with the case of treating aerobic organisms in one aeration tank. For this reason, a live bacterial SRT
(SRT ') becomes longer, stable treated water quality is obtained, and sludge settling property in the solid-liquid separator 12 is improved.

In the apparatus of FIG. 2, one aeration tank is divided into partition plates 13
Is divided into a first aeration tank 11a and a second aeration tank 11b by means of the first aeration tank 11a and the second aeration tank 11a.
b can also be configured as an independent aeration tank. In this case, even if the volume of the second aeration tank is small, the SRT of living bacteria can be lengthened, so the volume of the aeration tank as a whole becomes smaller than that in the case of obtaining an equivalent SRT in one aeration tank, It is advantageous in terms of additional space and cost. Further, although the separated sludge separated by the solid-liquid separation device 12 is subjected to ozone treatment, it is also possible to extract the in-tank liquid of the first aeration tank 11a to perform ozone treatment.

Test Example 1 The aerobic biological treatment was carried out as follows using the automobile plant integrated wastewater as the liquid to be treated. First, the treatment was performed by the apparatus of FIG. 4 for the first 25 days (comparative example), and then the apparatus of FIG. 2 was switched to the treatment of 35 days (example). The conditions and the quality of treated water are shown in Table 1. The SVI during the test period is shown in FIG.

[0046]

[Table 1] * 1 Average value from 10th to 25th day * 2 Average value from 40th to 60th day

As can be seen from the results of FIG. 3, the SVI of the input sludge at the start of operation (0th day) was about 160, but it increased with the operation and became about 400 after 25 days (comparative example). . After that, the SVI sharply decreased by switching to the process by the apparatus of FIG. 2, and after 15 days after the process switching, the good flock was around SVI 100 (Example). Further, as can be seen from the results in Table 1, in the comparative example, the water quality deteriorated, but in the example, stable treated water quality was obtained.

Test Example 2 The SRT (SRT ') of the live bacteria in Test Example 1 is determined by the above equation (a) as follows. SRT '(day) of Comparative Example: 3.5 SRT' (day) of Example: 6.3 As can be seen from the above results, it can be seen that SRT 'of the example is longer than that of the comparative example.

[0049]

The aerobic biological treatment apparatus of the present invention receives the organic effluent and the liquid mixture of the second aeration tank, mixes it with the biological sludge in the tank, and aerates the aeration tank. Aerating the reforming treatment device, and the reforming treatment sludge and return sludge,
Since it has a second aeration tank that returns this aeration liquid to the first aeration tank, it is possible to reduce the volume of surplus sludge, and also to suppress the expansion of installation space and construction cost, and a compact device. It is possible to obtain stable treated water quality and improve sludge settling property.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the principle of sludge volume reduction.

FIG. 2 is a systematic diagram showing an aerobic biological treatment apparatus of Example.

FIG. 3 is a graph showing the results of Test Example 1.

FIG. 4 is a system diagram showing a conventional aerobic biological treatment apparatus.

[Explanation of symbols]

1 aerobic biological treatment system 2 Modification system 3a Activated sludge 3b, 3e, 3g generated sludge 3c self-decomposition 3d breeding sludge 3f drawn sludge 3h mineralized part 3i increase part 4 Liquid to be treated 6 reforming sludge 7 excess sludge 8 Treatment liquid 11 aeration tank 11a First aeration tank 11b Second aeration tank 12 Solid-liquid separator 13 partition boards 14 flow paths 15 Air diffuser 15a First air diffuser 15b Second air diffuser 16 Air supply path 16a First air supply path 16b Second air supply path 17 Processed liquid path 18 connecting path 21 Processing liquid path 22 Separation sludge discharge path 23,36 pumps 24 Return sludge path 31 Ozone treatment tank 32 Extraction sludge path 33 Waste ozone path 34 Ozone supply path 35 Ozone treatment sludge path 37 Excess sludge discharge route

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-6-206088 (JP, A) JP-A-2-277597 (JP, A) JP-A-5-192679 (JP, A) JP-A-55- 192679 (JP, A) JP-A-4-90896 (JP, A) JP-B-57-19719 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 3/12 C02F 11 / 00-11/20

Claims (2)

(57) [Claims] 1. A mixed liquid of an organic drainage liquid and a second aeration tank.
A first aeration tank for receiving and aeration by mixing with the biological sludge in the tank, and a solid-liquid separation device for solid-liquid separating the mixed liquid of the first aeration tank into a separation liquid and separation sludge, A reforming treatment device for reforming a part of the separated sludge separated by the liquid separation device or a part of the mixed liquid of the first aeration tank to easily biodegradable, and the reforming treatment device. Return of reformed sludge and other part of separated sludge discharged from the solid-liquid separation device
An aerobic biological treatment apparatus for organic waste liquid, comprising: a second aeration tank that mixes sludge with aeration and returns the aeration liquid to the first aeration tank. 2. The aerobic biological treatment apparatus for organic waste liquid according to claim 1, wherein the reforming treatment apparatus is an ozone treatment apparatus.